The long-term goal of this research is to delineate the possible mechanisms underlying the increased abuse of substances, such as methamphetamine (METH), by individuals who are human immunodeficiency virus-1 (HIV)-positive. In this two-year exploratory project, we propose to specifically examine the synergistic effects of methamphetamine (METH), an addictive psychostimulant, and HIV-1 viral proteins on glial-neuronal induction of inflammation in the rat brain. In the central nervous system (CNS), the glial cells are infected by the HIV-1 virus, causing neuroinflammation. Increased inflammation in the brain has been correlated with neurodegenerative diseases and behavioral disorders, such as HIV-1 induced neurodegeneration (HAND) and HIV-1 induced dementia (HAD). Moreover, METH abuse in the HIV-infected individual can lead to increased viral loads and severe brain-related disorders. For these studies, we will use both the non-infectious HIV-1 transgenic (HIV-1Tg) rat and primary cell culture models. The HIV-1Tg rat carries a gag/pol deleted provirus gene, and expresses 7 out of 9 HIV-1 viral proteins. This HIV-1Tg rat develops clinical manifestations of human HIV disease, and, thus, mimics the infection that results from the persistent presence of HIV-1 proteins in HIV patients given anti-retroviral therapy. Recently, using PCR array analysis, we showed that the pro- inflammatory cytokine, IL-1, as well as the Ccl2, Ccl3, and Ccl7 chemokines, are increased to a greater extent in the brain of the HIV-1Tg rat compared to the F344 control rat. We have also demonstrated that there is elevated dopamine D1 receptor (D1R) expression in the prefrontal cortex of HIV-1Tg rats, and that these animals have greater METH-induced behavioral sensitization, as assessed by stereotypical head movement. Based on the literature and our previous data, we hypothesize that the abuse of substances, such as METH, in the presence of HIV-1 viral proteins, enhances glial activation, which affects neurons, and increases the activity of the dopaminergic system, thereby increasing the intake of METH. To test this hypothesis, we will first examine the glial-neuronal cell interaction in the brain of the HIV-1Tg rat with and without exposure to METH using immunohistochemistry. We will then identify gene expression changes in neurotransmitter activity, in particular, the dopaminergic system, as well as neuroinflammation-related markers. We will also isolate primary glial and neuronal cells from HIV-1Tg rats and examine gene expression changes in the dopaminergic and other neurotransmitter pathways, as well as inflammation, and apoptotic and oxidative stress markers after in vitro exposure to METH. Our specific aims include: 1) To determine the effects of METH and HIV viral proteins on glial and neuronal activation, neuroinflammation, and neurotransmitter modulation in the brain of the HIV-1Tg rat, and 2) To determine the effects of METH and HIV viral proteins on glial and neuronal activation, neuroinflammation, and neurotransmitter modulation in an ex vivo model using primary glial and neuronal cells isolated from the HIV- 1Tg rat brain To our knowledge, this proposal represents the first project to explore the effects of METH on glial-neuronal interactions and the subsequent effects on the dopaminergic system using the HIV-1Tg rat and primary cell cultures isolated from the HIV-1Tg rat. The data from this research will shed light on possible cellular and molecular mechanisms underlying the increased abuse of substances such as METH by HIV-positive individuals, and help to elucidate the glial-neuronal interactions associated with METH abuse and neuroAIDS. Our exploratory studies can also lead to better treatment approaches that will ultimately benefit both HIV-1 patients and substances abusers. Thus, the proposed studies have high clinical relevance and will contribute significantly to the understanding and treatment of neurological complications associated with substance abuse, HIV infection, and AIDS.